And tonight, there is a pilgrimage under way. Thousands of people headed to a great American city, whose steely resolve has been tested yet again. Boston. Firefighters killed in the line of duty. And tonight, their brothers are coming together from around the world to let that city know they are not alone. ABC's Linzie Janis is there with the outpouring tonight. Reporter: Thousands of firefighters from around the country and the world pouring into Boston today, lining up to pay their respects. And remember two of their own. This captain, traveling all the way from Los Angeles. Fire service has always been a brotherhood, sisterhood, and a we come out to keep that going and show our respects. Reporter: The city of Boston, watching the valiant fight Wednesday. Inside the inferno, 33-year-old Michael Kennedy, a former marine, and 43-year-old lieutenant Edward Walsh Jr., married and a father of three. Their actions would help save everyone in that four-story building. But they became trapped in the basement. It's tough to speak most times. Reporter: One witness to the blaze, star quarterback Tom Brady, who lived just doors away, and says he saw true courage. You realize who the real heroes are in this world. I feel so badly for the families, I just want to sate thank you from the bottom of my heart. Reporter: Today, a mountain of flowers. And at the church -- the line of firefighters goes on for miles. They're here to pay their respects and to support a city that's still healing from the marathon bombings. A city in mourning and Boston strong. Linzie Janis, ABC news, watertown, Massachusetts. And both men will be awarded the medal of valor from the firefighters of the city posthumously.

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